Coelacanths – living fossils

Until 1938, the coelacanth fish was thought extinct, but then fishermen off the coast of South Africa found a living coelacanth and things were never quite the same again.

The coelacanth present a fascinating story of the ways in which our knowledge of the world is sometimes increased by happenstance. Until 1938, coelacanths were only known as an order of peculiar lobe-finned fishes which appeared in the fossil record about 350 million years ago, about the same time the first creatures emerged from sea to land and were extinct for approximately 70 million years.

Then, in December of 1938, fishermen off the eastern coast of South Africa caught a living coelacanth. Though it didn’t look edible the captain of the boat decided to take the hundred and twenty-six pound, five foot long animal, with bulging blue eyes and heavy, bluish scales, back to port because it seemed so strange.

The curator at the local museum, Miss Courtenay Latimer, recognised the importance of the find and contacted Dr. J.L.B. Smith a leading South African ichthyologist. He identified it as a part of the “extinct” subclass of Crossopterygii, or “lobed-finned fish.” In terms of evolution, these ancient “fishes” are more closely related to land animals than to fish. The specimen’s paired fins are lobe-like and actually have jointed bones, like arms and legs.

Areas where the Coelacanths are found

For years after this unique finding, scientists searched for another specimen of this extraordinary fish. Fourteen years later, the “true” home of the living coelacanth, Latimeria chalumnae, was found in the Comoran archipelago in the western Indian Ocean.

Since that time about 200 specimens of have been caught in the Comoros. A few other specimens have also been caught near Madagascar and Mozambique, but genetic analyses suggest that these are simply “strays” from the main Comoros population.

The scientific community was shocked again in 1998 when UC Berkeley researchers announced the discovery of a coelacanth in North Sulawesi, Indonesia, almost 10,000 kilometers from the Comoros.

On 27 November 2000 a group of divers found 3 coelacanths off the Northeast coast of South Africa in KwaZulu Natal at Sodwana Bay, part of the St. Lucia Marine Protected Area, a world heritage site comprising a wetland and marine reserve known for its reefs and SCUBA diving.

The largest was between 1.5 m and 1.8 m long, the other two 1.2 m and 1 m. The group returned to Sodwana and dove successfully in 2001 observing 15 coelacanths, one pregnant. The Coelacanths were filmed and tissue samples were taken using a dart probe.

Behaviour

Coelacanths are nocturnal fish, and during the day, they are usually found in depths of 120-250 m, where they congregate in caves, with as many as 14 fish crowded together in a single cave. By resting in caves, they save energy and are also less vulnerable to large predators (deep-water sharks).

Each coelacanth has its own distinctive pattern of white markings, and this allows recognition of individuals and tracking of their movements. Although several individuals occupy overlapping home ranges, no aggressive encounters between coelacanths have been observed.